Dual-functional Mn-single atom catalysts for synergistic H₂O₂ generation and activation: Toward efficient refractory...

Electro-oxidation is a promising technology for treating refractory organic pollutants in landfill leachate but faces challenges of high energy consumption and inefficient degradation of complex organics. This study introduces a manganese single-atom catalyst (MnSAC) doped on carbon nanotubes (CNTs) within a gas-diffusion electrode to enhance electro-oxidation performance. The bifunctional catalyst simultaneously promotes 2e^- oxygen reduction reaction for H₂O₂ generation and in-situ activation of H₂O₂ to produce reactive oxygen species, primarily hydroxyl radicals (^•OH). In a system employing a Ni-Sb-SnO₂ anode and operating under the operation conditions (initial chemical oxygen demand: 478 mg L^-1; electrolyte: 0.1 mol L^-1 Na₂SO₄, current density: 10 mA cm^-2, volume: 100 mL), a 90 % removal rate (reduced to 49 mg L^-1) was achieved. The core innovation lies in the unique N-coordinated MnSAC (Mn-N₄) sites on CNTs, identified via density functional theory calculations to exhibit ΔG of -3.46 eV for H₂O₂ activation and organic adsorption. The Mn-N-C structure modulates the d-band center to optimize electron/charge distribution and transfer. This synergistic design: 1) enhances H₂O₂ activation and radical generation, 2) accelerates organic pollutant adsorption/degradation, and 3) improves reaction kinetics. The catalyst addresses critical issues like metal leaching and energy inefficiency, offering a robust, sustainable solution for refractory organic wastewater treatment.